Pumping cassette

ABSTRACT

A pump cassette is disclosed. The pump cassette includes housing. The housing includes at least one fluid inlet line and at least one fluid outlet line. Also, the cassette includes at least one reciprocating pressure displacement membrane pump within the housing. The pressure pump pumps at least one fluid from the fluid inlet line to at least one of the fluid outlet line. Also, the cassette includes at least one mixing chamber within the housing. The mixing chamber is fluidly connected to the fluid outlet line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/871,787, filed on Oct. 12, 2007, which claims priority from the following United States Provisional patent applications:

U.S. Provisional Patent Application No. 60/904,024 filed on Feb. 27, 2007; and

U.S. Provisional Patent Application No. 60/921,314 filed on Apr. 2, 2007. Each of the three above-indicated priority applications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a pumping cassette for pumping fluid.

SUMMARY OF THE INVENTION

In accordance with one aspect of the pump cassette the cassette includes housing. The housing includes at least one fluid inlet line and at least one fluid outlet line. Also, the cassette includes at least one reciprocating pressure displacement membrane pump within the housing. The pressure pump pumps at least one fluid from the fluid inlet line to at least one of the fluid outlet line. Also, the cassette includes at least one mixing chamber within the housing. The mixing chamber is fluidly connected to the fluid outlet line.

Various embodiments of this aspect of the cassette include one or more of the following. Where the reciprocating pressure displacement pump includes a curved rigid chamber wall and a flexible membrane attached to the rigid chamber wall. The flexible membrane and the rigid chamber wall define a pumping chamber. Where the cassette housing includes a top plate, a midplate and a bottom plate. Where the cassette also includes at least one valve. In some embodiments, the at least one valve includes a valve housing having a membrane. The membrane divides the housing into two chambers. Where the mixing chamber includes a curved rigid chamber wall having at least one fluid inlet and at least one fluid outlet. Where the cassette also includes at least one metering membrane pump within the housing. The metering pump fluidly connects to the mixing chamber on the housing and to a metering pump fluid line. The metering pump fluid line is fluidly connected to the at least one of the at least one fluid inlet lines. Some embodiments of the metering pump include where the fluid line is connected to at second fluid inlet line.

In accordance with another aspect of the pump cassette the cassette includes a housing including at least two fluid inlet lines and at least one fluid outlet line. Also included is at least one reciprocating pressure displacement membrane pump within the housing. The pressure pump pumps a fluid from at least one of the fluid inlet line to at least one of the fluid outlet line. The cassette also includes at least one mixing chamber within the housing, the mixing chamber fluidly connected to the fluid outlet line. Also included is at least one metering membrane pump within the housing. The metering membrane pump fluidly connects to the mixing chamber on the housing and to a metering pump fluid line. The metering pump fluid line is fluidly connected to the at least one of the at least two fluid inlet lines.

Various embodiments of this aspect of the cassette include one or more of the following. Where the reciprocating pressure displacement pump includes a curved rigid chamber wall and a flexible membrane attached to the rigid chamber wall. The flexible membrane and the rigid chamber wall define a pumping chamber. Where the cassette housing includes a top plate, a midplate and a bottom plate. Where the mixing chamber includes a curved rigid chamber wall having at least one fluid inlet and at least one fluid outlet. Where the cassette further includes at least one valve. In some embodiments, the valve includes a valve housing having a membrane dividing the housing into two chambers.

In accordance with another aspect of the pump cassette includes a housing. The housing includes at least three fluid inlet lines and at least one fluid outlet line. The cassette also includes at least two reciprocating pressure displacement membrane pumps within the housing that pump a fluid from at least one of the fluid inlet lines to at least one of the fluid outlet line. Also, the cassette includes at least one mixing chamber within the housing that is fluidly connected to the fluid outlet line. The cassette also includes at least two metering membrane pumps within the housing. The metering pumps are fluidly connected to respective fluid inlet lines and to the mixing chamber on the housing. The metering pumps pump a volume of a respective fluid from the fluid inlet lines to a fluid line fluidly connected to the mixing chamber.

Various embodiments of this aspect of the cassette include one or more of the following. Where the reciprocating pressure displacement pump includes a curved rigid chamber wall and a flexible membrane attached to the rigid chamber wall. The flexible membrane and the rigid chamber wall define a pumping chamber. Where the cassette housing includes a top plate, a midplate and a bottom plate. Where the cassette includes at least one valve. Some embodiments include where the valve includes a valve housing having a membrane, the membrane dividing the housing into two chambers.

These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the appended claims and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein:

FIG. 1A is a sectional view of one embodiment of a pod-pump that is incorporated into embodiments of cassette;

FIG. 1B is a sectional view of an exemplary embodiment of a pod pump that is incorporated into embodiments of the cassette;

FIG. 2A is an illustrative sectional view of one embodiment of one type of pneumatically controlled valve that is incorporated into some embodiments of the cassette;

FIG. 2B is a sectional view of another embodiment of one type of pneumatically controlled valve that is incorporated into some embodiments of the cassette;

FIG. 2C is a sectional view of another embodiment of one type of pneumatically controlled valve that is incorporated into some embodiments of the cassette;

FIG. 2D is a sectional view of another embodiment of one type of pneumatically controlled valve that is incorporated into some embodiments of the cassette;

FIGS. 2E-2F are top and bottom views of embodiments of the valving membrane;

FIG. 2G shows pictorial, top and cross sectional views of one embodiment of the valving membrane;

FIG. 3 is a sectional view of a pod pump within a cassette;

FIG. 4 is a sectional view of a pod pump within a cassette having a variable membrane;

FIGS. 4A and 4B are top and section views respectively of a pod pump within a cassette having a dimpled/variable membrane;

FIGS. 4C and 4D are pictorial views of a single ring membrane with a variable surface;

FIGS. 5A-5D are side views of various embodiments of variable membranes;

FIGS. 5E-5H are pictorial views of various embodiments of the metering pump membrane;

FIGS. 6A and 6B are pictorial views of a double ring membrane with a smooth surface;

FIGS. 6C and 6D are pictorial views of a double ring membrane with a dimple surface;

FIGS. 6E and 6F are pictorial views of double ring membranes with variable surfaces;

FIG. 6G is a cross sectional view of a double ring membrane with a variable surface;

FIG. 7 is a schematic showing a pressure actuation system that may be used to actuate a pod pump;

FIG. 8 is one embodiment of the fluid flow-path schematic of the cassette;

FIG. 9 is an alternate embodiment fluid flow-path schematic for an alternate embodiment of the cassette;

FIG. 10 is an isometric front view of the exemplary embodiment of the actuation side of the midplate of the cassette with the valves indicated corresponding to FIG. 8;

FIG. 11A are front and isometric views of the exemplary embodiment of the outer top plate of the cassette;

FIG. 11B are front and isometric views of the exemplary embodiment of the inner top plate of the cassette;

FIG. 11C is a side view of the exemplary embodiment of the top plate of the cassette;

FIG. 12A are front and isometric views of the exemplary embodiment of the fluid side of the midplate of the cassette;

FIG. 12B are front and isometric views of the exemplary embodiment of the air side of the midplate of the cassette;

FIG. 12C is a side view of the exemplary embodiment of the midplate of the cassette;

FIG. 13A are front and isometric views of the exemplary embodiment of the inner side of the bottom plate of the cassette;

FIG. 13B are front and isometric views of the exemplary embodiment of the outer side of the bottom plate of the cassette;

FIG. 13C is a side view of the exemplary embodiment of the midplate of the cassette;

FIG. 14A is a top view of the assembled exemplary embodiment of the cassette;

FIG. 14B is a bottom view of the assembled exemplary embodiment of the cassette;

FIG. 14C is an exploded view of the assembled exemplary embodiment of the cassette;

FIG. 14D is an exploded view of the assembled exemplary embodiment of the cassette;

FIGS. 15A-15C show cross sectional views of the exemplary embodiment of the assembled cassette;

FIG. 16A show isometric and top views of an alternate embodiment of the top plate according to an alternate embodiment of the cassette;

FIG. 16B show bottom views of an alternate embodiment of the top plate according to an alternate embodiment of the cassette;

FIG. 16C shows a side view of the alternate embodiment of the top plate;

FIG. 17A show isometric and top views of an alternate embodiment of the midplate according to an alternate embodiment of the cassette;

FIG. 17B show isometric and bottom views of an alternate embodiment of the midplate according to an alternate embodiment of the cassette;

FIG. 17C shows a side view of the alternate embodiment of the midplate;

FIG. 18A show isometric and top views of an alternate embodiment of the bottom plate according to an alternate embodiment of the cassette;

FIG. 18B show isometric and bottom views of an alternate embodiment of the bottom according to an alternate embodiment of the cassette;

FIG. 18C shows a side view of the alternate embodiment of the bottom plate;

FIG. 19A is a top view of an assembled alternate embodiment of the cassette;

FIG. 19B is an exploded view of the assembled alternate embodiment of the cassette;

FIG. 19C is an exploded view of the assembled alternate embodiment of the cassette; and

FIGS. 20A-20B shows a cross sectional view of the exemplary embodiment of the assembled cassette.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 1. Pumping Cassette

1.1 Cassette

The pumping cassette includes various features, namely, pod pumps, fluid lines and in some embodiment, valves. The cassette embodiments shown and described in this description include exemplary and some alternate embodiments. However, any variety of cassettes having a similar functionality is contemplated. As well, although the cassette embodiments described herein are implementations of the fluid schematics as shown in FIGS. 8 and 9, in other embodiments, the cassette may have varying fluid paths and/or valve placement and/or pod pump placements and numbers and thus, is still within the scope of the invention.

In the exemplary embodiment, the cassette includes a top plate, a midplate and a bottom plate. There are a variety of embodiments for each plate. In general, the top plate includes pump chambers and fluid lines, the midplate includes complementary fluid lines, metering pumps and valves and the bottom plate includes actuation chambers (and in some embodiments, the top plate and the bottom plate include complementary portions of a balancing chamber).

In general, the membranes are located between the midplate and the bottom plate, however, with respect to balancing chambers, a portion of a membrane is located between the midplate and the top plate. Some embodiments include where the membrane is attached to the cassette, either overmolded, captured, bonded, press fit, welded in or any other process or method for attachment, however, in the exemplary embodiments, the membranes are separate from the top plate, midplate and bottom plate until the plates are assembled.

The cassettes may be constructed of a variety of materials. Generally, in the various embodiment, the materials used are solid and non flexible. In the preferred embodiment, the plates are constructed of polysulfone, but in other embodiments, the cassettes are constructed of any other solid material and in exemplary embodiment, of any thermoplastic or thermoset.

In the exemplary embodiment, the cassettes are formed by placing the membranes in their correct locations, assembling the plates in order and connecting the plates. In one embodiment, the plates are connected using a laser welding technique. However, in other embodiments, the plates may be glued, mechanically fastened, strapped together, ultrasonically welded or any other mode of attaching the plates together.

In practice, the cassette may be used to pump any type of fluid from any source to any location. The types of fluid include nutritive, normutritive, inorganic chemicals, organic chemicals, bodily fluids or any other type of fluid. Additionally, fluid in some embodiments include a gas, thus, in some embodiments, the cassette is used to pump a gas.

The cassette serves to pump and direct the fluid from and to the desired locations. In some embodiments, outside pumps pump the fluid into the cassette and the cassette pumps the fluid out. However, in some embodiments, the pod pumps serve to pull the fluid into the cassette and pump the fluid out of the cassette.

As discussed above, depending on the valve locations, control of the fluid paths is imparted. Thus, the valves being in different locations or additional valves are alternate embodiments of this cassette. Additionally, the fluid lines and paths shown in the figures described above are mere examples of fluid lines and paths. Other embodiments may have more, less and/or different fluid paths. In still other embodiments, valves are not present in the cassette.

The number of pod pumps described above may also vary depending on the embodiment. For example, although the exemplary and alternate embodiments shown and described above include two pod pumps, in other embodiments, the cassette includes one. In still other embodiments, the cassette includes more than two pod pumps. The pod pumps can be single pumps or work in tandem to provide a more continuous flow. Either or both may be used in various embodiments of the cassette.

The various fluid inlets and fluid outlets are fluid ports. In practice, depending on the valve arrangement and control, a fluid inlet can be a fluid outlet. Thus, the designation of the fluid port as a fluid inlet or a fluid outlet is only for description purposes. The various embodiments have interchangeable fluid ports. The fluid ports are provided to impart particular fluid paths onto the cassette. These fluid ports are not necessarily all used all of the time; instead, the variety of fluid ports provides flexibility of use of the cassette in practice. 1.2 Exemplary Pressure Pod Pump Embodiments

FIG. 1A is a sectional view of an exemplary pod pump 100 that is incorporated into a fluid control or pump cassette (see also FIGS. 3 and 4), in accordance with an exemplary embodiment of the cassette. In this embodiment, the pod pump is formed from three rigid pieces, namely a “top” plate 106, a midplate 108, and a “bottom” plate 110 (it should be noted that the terms “top” and “bottom” are relative and are used here for convenience with reference to the orientation shown in FIG. 1A). The top and bottom plates 106 and 110 include generally hemispheroid portions that when assembled together define a hemispheroid chamber, which is a pod pump 100.

A membrane 112 separates the central cavity of the pod pump into two chambers. In one embodiment, these chambers are: the pumping chamber that receives the fluid to be pumped and an actuation chamber for receiving the control gas that pneumatically actuates the pump. An inlet 102 allows fluid to enter the pumping chamber, and an outlet 104 allows fluid to exit the pumping chamber. The inlet 102 and the outlet 104 may be formed between midplate 108 and the top plate 106. Pneumatic pressure is provided through a pneumatic port 114 to either force, with positive gas pressure, the membrane 112 against one wall of the pod pump cavity to minimize the pumping chamber's volume, or to draw, with negative gas pressure, the membrane 112 towards the other wall of the pod pump 100 cavity to maximize the pumping chamber's volume.

The membrane 112 is provided with a thickened rim 116, which is held tightly by a protrusion 118 in the midplate 108. Thus, in manufacturing, the membrane 112 can be placed in and held by the groove 108 before the bottom plate 110 is connected (in the exemplary embodiment) to the midplate 108.

Although not shown in FIGS. 1A and 1B, in some embodiments of the pod pump, on the fluid side, a groove is present on the chamber wall. The groove acts to prevent folds in the membrane from trapping fluid in the chamber when emptying.

Referring first to FIG. 1A a cross sectional view of a reciprocating positive-displacement pump 100 in a cassette is shown. The pod pump 100 includes a flexible membrane 112 (also referred to as the “pump diaphragm” or “membrane”) mounted where the pumping chamber (also referred to as a “liquid chamber” or “liquid pumping chamber”) wall 122 and the actuation chamber (also referred to as the “pneumatic chamber”) wall 120 meet. The membrane 112 effectively divides that interior cavity into a variable-volume pumping chamber (defined by the rigid interior surface of the pumping chamber wall 122 and a surface of the membrane 112) and a complementary variable-volume actuation chamber (defined by the rigid interior surface of the actuation chamber wall 120 and a surface of the membrane 112). The top portion 106 includes a fluid inlet 102 and a fluid outlet 104, both of which are in fluid communication with the pumping/liquid chamber. The bottom portion 110 includes an actuation or pneumatic interface 114 in fluid communication with the actuation chamber. As discussed in greater detail below, the membrane 112 can be urged to move back and forth within the cavity by alternately applying negative or vent to atmosphere and positive pneumatic pressure at the pneumatic interface 114. As the membrane 112 reciprocates back and forth, the sum of the volumes of the pumping and actuation chambers remains constant.

During typical fluid pumping operations, the application of negative or vent to atmosphere pneumatic pressure to the actuation or pneumatic interface 114 tends to withdraw the membrane 112 toward the actuation chamber wall 120 so as to expand the pumping/liquid chamber and draw fluid into the pumping chamber through the inlet 102, while the application of positive pneumatic pressure tends to push the membrane 112 toward the pumping chamber wall 122 so as to collapse the pumping chamber and expel fluid in the pumping chamber through the outlet 104. During such pumping operations, the interior surfaces of the pumping chamber wall 122 and the actuation chamber wall 120 limit movement of the membrane 112 as it reciprocates back and forth. In the embodiment shown in FIG. 1A, the interior surfaces of the pumping chamber wall 122 and the actuation chamber wall 120 are rigid, smooth, and hemispherical. In lieu of a rigid actuation chamber wall 120, an alternative rigid limit structure—for example, a portion of a bezel used for providing pneumatic pressure and/or a set of ribs—may be used to limit the movement of the membrane as the pumping chamber approaches maximum value. Bezels and rib structures are described generally in U.S. patent application Ser. No. 10/697,450 entitled BEZEL ASSEMBLY FOR PNEUMATIC CONTROL filed on Oct. 30, 2003 and published as Publication No. US 2005/0095154 (Attorney Docket No. 1062/D75) and related PCT Application No. PCT/US2004/035952 entitled BEZEL ASSEMBLY FOR PNEUMATIC CONTROL filed on Oct. 29, 2004 and published as Publication No. WO 2005/044435 (Attorney Docket No. 1062/D71WO), both of which are hereby incorporated herein by reference in their entireties. Thus, the rigid limit structure—such as the rigid actuation chamber wall 120, a bezel, or a set of ribs—defines the shape of the membrane 112 when the pumping chamber is at its maximum value. In a preferred embodiment, the membrane 112 (when urged against the rigid limit structure) and the rigid interior surface of the pumping chamber wall 122 define a spherical pumping chamber volume when the pumping chamber volume is at a minimum.

Thus, in the embodiment shown in FIG. 1A, movement of the membrane 112 is limited by the pumping chamber wall 122 and the actuation chamber wall 120. As long as the positive and vent to atmosphere or negative pressurizations provided through the pneumatic port 114 are strong enough, the membrane 112 will move from a position limited by the actuation chamber wall 120 to a position limited by the pumping chamber wall 122. When the membrane 112 is forced against the actuation chamber wall 120, the membrane and the pumping chamber wall 122 define the maximum volume of the pumping chamber. When the membrane is forced against the pumping chamber wall 122, the pumping chamber is at its minimum volume.

In an exemplary embodiment, the pumping chamber wall 122 and the actuation chamber wall 120 both have a hemispheroid shape so that the pumping chamber will have a spheroid shape when it is at its maximum volume. By using a pumping chamber that attains a spheroid shape—and particularly a spherical shape—at maximum volume, circulating flow may be attained throughout the pumping chamber. Such shapes accordingly tend to avoid stagnant pockets of fluid in the pumping chamber. As discussed further below, the orientations of the inlet 102 and outlet 104 also tend to have an impact on the flow of fluid through the pumping chamber and in some embodiments, reduce the likelihood of stagnant pockets of fluid forming. Additionally, compared to other volumetric shapes, the spherical shape (and spheroid shapes in general) tends to create less shear and turbulence as the fluid circulates into, through, and out of the pumping chamber.

Referring now to FIGS. 3-4, a raised flow path 30 is shown in the pumping chamber. This raised flow path 30 allows for the fluid to continue flowing through the pod pumps after the membrane reaches the end of stroke. Thus, the raised flow path 30 minimizes the chances of the membrane causing air or fluid to be trapped in the pod pump or the membrane blocking the inlet or outlet of the pod pump which would inhibit continuous flow. The raised flow path 30 is shown in the exemplary embodiment having particular dimensions, however, in alternate embodiments, as seen in FIGS. 18A-18E, the raised flow path 30 is narrower, or in still other embodiments, the raised flow path 30 can be any dimensions as the purpose is to control fluid flow so as to achieve a desired flow rate or behavior of the fluid. Thus, the dimensions shown and described here with respect to the raised flow path, the pod pumps, the valves or any other aspect are mere exemplary and alternate embodiments. Other embodiments are readily apparent.

1.3 Exemplary Balancing Pods Embodiment

Referring now to FIG. 1B, an exemplary embodiment of a balancing pod is shown. The balancing pod is constructed similar to the pod pump described above with respect to FIG. 1A. However, a balancing pod includes two fluid balancing chambers, rather than an actuation chamber and a pumping chamber, and does not include an actuation port. Additionally, each balancing chamber includes an inlet 102 and an outlet 104. In the exemplary embodiment, a groove 126 is included on each of the balancing chamber walls 120, 122. The groove 126 is described in further detail below.

The membrane 112 provides a seal between the two chambers. The balancing chambers work to balance the flow of fluid into and out of the chambers such that both chambers maintain an equal volume rate flow. Although the inlets 102 and outlets 104 for each chamber are shown to be on the same side, in other embodiments, the inlets 102 and outlets 104 for each chamber are on different sides. Also, the inlets 102 and outlets 104 can be on either side, depending on the flow path in which the balancing chamber is integrated.

In one embodiment of the balancing chambers the membrane 112 includes an embodiment similar to the one described below with respect to FIG. 6A-6G. However, in alternate embodiments, the membrane 112 can be over molded or otherwise constructed such that a double-ring seal is not applicable.

1.4 Metering Pumps and Fluid Management System

The metering pump can be any pump that is capable of adding any fluid or removing any fluid. The fluids include but are not limited to pharmaceuticals, inorganic compounds or elements, organic compounds or elements, nutraceuticals, nutritional elements or compounds or solutions, or any other fluid capable of being pumped. In one embodiment, the metering pump is a membrane pump. In the exemplary embodiment, the metering pump is a smaller volume pod pump. In the exemplary embodiment, the metering pump includes an inlet and an outlet, similar to a larger pod pump (as shown in FIG. 1A for example). However, the inlet and outlet are generally much smaller than a pod pump and, in one exemplary embodiment, includes a volcano valve-like raised ring around either the inlet or outlet. Metering pumps include a membrane, and various embodiments of a metering pump membrane are shown in FIGS. 5E-5H. The metering pump, in some embodiments, pumps a volume of fluid out of the fluid line. Once the fluid is in the pod pump, a reference chamber, located outside the cassette, using the FMS, determines the volume that has been removed.

Thus, depending on the embodiment, this volume of fluid that has been removed will not then flow to the fluid outlet, the balance chambers or to a pod pump. Thus, in some embodiments, the metering pump is used to remove a volume of fluid from a fluid line. In other embodiments, the metering pump is used to remove a volume of fluid to produce other results.

FMS may be used to perform certain fluid management system measurements, such as, for example, measuring the volume of subject fluid pumped through the pump chamber during a stroke of the membrane or detecting air in the pumping chamber, e.g., using techniques described in U.S. Pat. Nos. 4,808,161; 4,826,482; 4,976,162; 5,088,515; and 5,350,357, which are hereby incorporated herein by reference in their entireties.

Metering pumps are also used in various embodiments to pump a second fluid into the fluid line. In some embodiments, the metering pump is used to pump a therapeutic or a compound into a fluid line. One embodiment uses the metering pump to pump a volume of compound into a mixing chamber in order to constitute a solution. In some of these embodiments, the metering pumps are configured for FMS volume measurement. In other embodiments, the metering pumps are not.

For FMS measurement, a small fixed reference air chamber is located outside of the cassette, for example, in the pneumatic manifold (not shown). A valve isolates the reference chamber and a second pressure sensor. The stroke volume of the metering pump may be precisely computed by charging the reference chamber with air, measuring the pressure, and then opening the valve to the pumping chamber. The volume of air on the chamber side may be computed based on the fixed volume of the reference chamber and the change in pressure when the reference chamber was connected to the pump chamber.

1.5 Valves

The exemplary embodiment of the cassette includes one or more valves. Valves are used to regulate flow by opening and closing fluid lines. The valves included in the various embodiments of the cassette include one or more of the following: volcano valves or smooth valves. In some embodiment of the cassette, check valves may be included. Embodiments of the volcano valve are shown in FIGS. 2A and 2B, while an embodiment of the smooth valve is shown in FIG. 2C. Additionally, FIGS. 3 and 4 show cross sections of one embodiment of a pod pump in a cassette with an inlet and an outlet valve.

Generally speaking, reciprocating positive-displacement pumps of the types just described may include, or may be used in conjunction with, various valves to control fluid flow through the pump. Thus, for example, the reciprocating positive-displacement pump or the balancing pods may include, or be used in conjunction with, an inlet valve and/or an outlet valve. The valves may be passive or active. In the exemplary embodiment of the reciprocating positive-displacement pump the membrane is urged back and forth by positive and negative pressurizations, or by positive and vent to atmosphere pressurizations, of a gas provided through the pneumatic port, which connects the actuation chamber to a pressure actuation system. The resulting reciprocating action of the membrane pulls fluid into the pumping chamber from the inlet (the outlet valve prevents liquid from being sucked back into the pumping chamber from the outlet) and then pushes the fluid out of the pumping chamber through the outlet (the inlet valve prevents fluid from being forced back from the inlet).

In the exemplary embodiments, active valves control the fluid flow through the pump(s) and the cassette. The active valves may be actuated by a controller in such a manner as to direct flow in a desired direction. Such an arrangement would generally permit the controller to cause flow in either direction through the pod pump. In a typical system, the flow would normally be in a first direction, e.g., from the inlet to the outlet. At certain other times, the flow may be directed in the opposite direction, e.g., from the outlet to the inlet. Such reversal of flow may be employed, for example, during priming of the pump, to check for an aberrant line condition (e.g., a line occlusion, blockage, disconnect, or leak), or to clear an aberrant line condition (e.g., to try to dislodge a blockage).

Pneumatic actuation of valves provides pressure control and a natural limit to the maximum pressure that may be developed in a system. In the context of a system, pneumatic actuation has the added benefit of providing the opportunity to locate all the solenoid control valves on one side of the system away from the fluid paths.

Referring now to FIGS. 2A and 2B, sectional views of two embodiments of a volcano valve are shown. The volcano valves are pneumatically controlled valves that may be used in embodiments of the cassette. A membrane 202, along with the midplate 204, defines a valving chamber 206. Pneumatic pressure is provided through a pneumatic port 208 to either force, with positive gas pressure, the membrane 202 against a valve seat 210 to close the valve, or to draw, with negative gas pressure, or in some embodiments, with vent to atmospheric pressure, the membrane away from the valve seat 210 to open the valve. A control gas chamber 212 is defined by the membrane 202, the top plate 214, and the midplate 204. The midplate 204 has an indentation formed on it, into which the membrane 202 is placed so as to form the control gas chamber 212 on one side of the membrane 202 and the valving chamber 206 on the other side.

The pneumatic port 208 is defined by a channel formed in the top plate 214. By providing pneumatic control of several valves in a cassette, valves can be ganged together so that all the valves ganged together can be opened or closed at the same time by a single source of pneumatic pressure. Channels formed on the midplate 204, corresponding with fluid paths along with the bottom plate 216, define the valve inlet 218 and the valve outlet 220. Holes formed through the midplate 204 provide communication between the inlet 218 and the valving chamber 206 and between the valving chamber 206 and the outlet 220.

The membrane 202 is provided with a thickened rim 222, which fits tightly in a groove 224 in the midplate 204. Thus, the membrane 202 can be placed in and held by the groove 224 before the top plate 214 is connected to the midplate 204. Thus, this valve design may impart benefits in manufacturing. As shown in FIGS. 2B and 2C, the top plate 214 may include additional material extending into control gas chamber 212 so as to prevent the membrane 202 from being urged too much in a direction away from the groove 224, so as to prevent the membrane's thickened rim 222 from popping out of the groove 224. The location of the pneumatic port 208 with respect to the control gas chamber 212 varies in the two embodiments shown in FIGS. 2A and 2B.

FIG. 2C shows an embodiment in which the valving chamber lacks a valve seat feature. Rather, in FIG. 2C, the valve in this embodiment does not include any volcano features and thus, the valving chamber 206, i.e., the fluid side, does not include any raised features and thus is smooth. This embodiment is used in cassettes used to pump fluid sensitive to shearing. FIG. 2D shows an embodiment in which the valving chamber has a raised area to aid in the sealing of the valving membrane. Referring now to FIGS. 2E-2G, various embodiments of the valve membrane are shown. Although some exemplary embodiments have been shown and described, in other embodiments, variations of the valve and valving membrane may be used.

1.6 Exemplary Embodiments of the Pod Membrane

In some embodiments, the membrane has a variable cross-sectional thickness, as shown in FIG. 4. Thinner, thicker or variable thickness membranes may be used to accommodate the strength, flexural and other properties of the chosen membranes materials. Thinner, thicker or variable membrane wall thickness may also be used to manage the membrane thereby encouraging it to flex more easily in some areas than in other areas, thereby aiding in the management of pumping action and flow of subject fluid in the pump chamber. In this embodiment the membrane is shown having its thickest cross-sectional area closest to its center. However in other embodiments having a membrane with a varying cross-sectional, the thickest and thinnest areas may be in any location on the membrane. Thus, for example, the thinner cross-section may be located near the center and the thicker cross-sections located closer to the perimeter of the membrane. Still other configurations are possible. Referring to FIGS. 5A-5D, one embodiment of a membrane is shown having various surface embodiments, these include smooth (FIG. 5A), rings (FIG. 5D), ribs (FIG. 5C), dimples or dots (FIG. 5B) of variable thickness and or geometry located at various locations on the actuation and or pumping side of the membrane. In one embodiment of the membrane, the membrane has a tangential slope in at least one section, but in other embodiments, the membrane is completely smooth or substantially smooth.

Referring now to FIGS. 4A, 4C and 4D, an alternate embodiment of the membrane is shown. In this embodiment, the membrane has a dimpled or dotted surface.

The membrane may be made of any flexible material having a desired durability and compatibility with the subject fluid. The membrane can be made from any material that may flex in response to fluid, liquid or gas pressure or vacuum applied to the actuation chamber. The membrane material may also be chosen for particular bio-compatibility, temperature compatibility or compatibility with various subject fluids that may be pumped by the membrane or introduced to the chambers to facilitate movement of the membrane. In the exemplary embodiment, the membrane is made from high elongation silicone. However, in other embodiments, the membrane is made from any elastomer or rubber, including, but not limited to, silicone, urethane, nitrile, EPDM or any other rubber, elastomer or flexible material.

The shape of the membrane is dependent on multiple variables. These variables include, but are not limited to: the shape of the chamber; the size of the chamber; the subject fluid characteristics; the volume of subject fluid pumped per stroke; and the means or mode of attachment of the membrane to the housing. The size of the membrane is dependent on multiple variables. These variables include, but are not limited to: the shape of the chamber; the size of the chamber; the subject fluid characteristics; the volume of subject fluid pumped per stroke; and the means or mode of attachment of the membrane to the housing. Thus, depending on these or other variables, the shape and size of the membrane may vary in various embodiments.

The membrane can have any thickness. However, in some embodiments, the range of thickness is between 0.002 inches to 0.125 inches. Depending on the material used for the membrane, the desired thickness may vary. In one embodiment, high elongation silicone is used in a thickness ranging from 0.015 inches to 0.050 inches. However in other embodiments, the thickness may vary.

In the exemplary embodiment, the membrane is pre-formed to include a substantially dome-shape in at least part of the area of the membrane. One embodiment of the dome-shaped membrane is shown in FIGS. 4E and 4F. Again, the dimensions of the dome may vary based on some or more of the variables described above. However, in other embodiments, the membrane may not include a pre-formed dome shape.

In the exemplary embodiment, the membrane dome is formed using liquid injection molding. However, in other embodiments, the dome may be formed by using compression molding. In alternate embodiments, the membrane is substantially flat. In other embodiments, the dome size, width or height may vary.

In various embodiments, the membrane may be held in place by various means and methods. In one embodiment, the membrane is clamped between the portions of the cassette, and in some of these embodiments, the rim of the cassette may include features to grab the membrane. In others of this embodiment, the membrane is clamped to the cassette using at least one bolt or another device. In another embodiment, the membrane is over-molded with a piece of plastic and then the plastic is welded or otherwise attached to the cassette. In another embodiment, the membrane is pinched between the mid plate described with respect to FIGS. 1A and 1B and the bottom plate. Although some embodiments for attachment of the membrane to the cassette are described, any method or means for attaching the membrane to the cassette can be used. The membrane, in one alternate embodiment, is attached directly to one portion of the cassette. In some embodiments, the membrane is thicker at the edge, where the membrane is pinched by the plates, than in other areas of the membrane. In some embodiments, this thicker area is a gasket, in some embodiments an O-ring, ring or any other shaped gasket. Referring again to 6A-6D, one embodiment of the membrane is shown with two gaskets 62, 64. In some of these embodiments, the gasket(s) 62, 64 provides the attachment point of the membrane to the cassette. In other embodiments, the membrane includes more than two gaskets. Membranes with one gasket are also included in some embodiments (see FIGS. 4A-4D).

In some embodiments of the gasket, the gasket is contiguous with the membrane. However, in other embodiments, the gasket is a separate part of the membrane. In some embodiments, the gasket is made from the same material as the membrane. However, in other embodiments, the gasket is made of a material different from the membrane. In some embodiments, the gasket is formed by over-molding a ring around the membrane. The gasket can be any shape ring or seal desired so as to complement the pod pump housing embodiment. In some embodiments, the gasket is a compression type gasket.

1.7 Mixing Pods

Some embodiments of the cassette include a mixing pod. A mixing pod includes a chamber for mixing. In some embodiments, the mixing pod is a flexible structure, and in some embodiments, at least a section of the mixing pod is a flexible structure. The mixing pod can include a seal, such as an o-ring, or a membrane. The mixing pod can be any shape desired. In the exemplary embodiment, the mixing pod is similar to a pod pump except it does not include a membrane and does not include an actuation port. Some embodiments of this embodiment of the mixing pod include an o-ring seal to seal the mixing pod chamber. Thus, in the exemplary embodiment, the mixing pod is a spherical hollow pod with a fluid inlet and a fluid outlet. As with the pod pumps, the chamber size can be any size desired.

2. Pressure Pump Actuation System

FIG. 7 is a schematic showing an embodiment of a pressure actuation system that may be used to actuate a pod pump with both positive and negative pressure, such as the pod pump shown in FIG. 1A. The pressure actuation system is capable of intermittently or alternately providing positive and negative pressurizations to the gas in the actuation chamber of the pod pump. However, in some embodiments, FIG. 7 does not apply in these embodiments, actuation of the pod pump is accomplished by applying positive pressure and vent to atmosphere (again, not shown in FIG. 7). The pod pump—including the flexible membrane, the inlet, the outlet, the pneumatic port, the pumping chamber, the actuation chamber, and possibly including an inlet check valve and an outlet check valve or other valves—is part of a larger disposable system. The pneumatic actuation system—including an actuation-chamber pressure transducer, a positive-supply valve, a negative-supply valve, a positive-pressure gas reservoir, a negative-pressure gas reservoir, a positive-pressure-reservoir pressure transducer, a negative-pressure-reservoir pressure transducer, as well as an electronic controller including, in some embodiments, a user interface console (such as a touch-panel screen)—may be part of a base unit.

The positive-pressure reservoir provides to the actuation chamber the positive pressurization of a control gas to urge the membrane towards a position where the pumping chamber is at its minimum volume (i.e., the position where the membrane is against the rigid pumping-chamber wall). The negative-pressure reservoir provides to the actuation chamber the negative pressurization of the control gas to urge the membrane in the opposite direction, towards a position where the pumping chamber is at its maximum volume (i.e., the position where the membrane is against the rigid actuation-chamber wall).

A valving mechanism is used to control fluid communication between each of these reservoirs and the actuation chamber. As shown in FIG. 7, a separate valve is used for each of the reservoirs; a positive-supply valve controls fluid communication between the positive-pressure reservoir and the actuation chamber, and a negative-supply valve controls fluid communication between the negative-pressure reservoir and the actuation chamber. These two valves are controlled by the controller. Alternatively, a single three-way valve may be used in lieu of the two separate valves. The valves may be binary on-off valves or variable-restriction valves.

The controller also receives pressure information from the three pressure transducers: an actuation-chamber pressure transducer, a positive-pressure-reservoir pressure transducer, and a negative-pressure-reservoir pressure transducer. As their names suggest, these transducers respectively measure the pressure in the actuation chamber, the positive-pressure reservoir, and the negative-pressure reservoir. The actuation-chamber-pressure transducer is located in a base unit but is in fluid communication with the actuation chamber through the pod pump pneumatic port. The controller monitors the pressure in the two reservoirs to ensure they are properly pressurized (either positively or negatively). In one exemplary embodiment, the positive-pressure reservoir may be maintained at around 750 mmHG, while the negative-pressure reservoir may be maintained at around −450 mmHG.

Still referring to FIG. 7, a compressor-type pump or pumps (not shown) may be used to maintain the desired pressures in these reservoirs. For example, two independent compressors may be used to respectively service the reservoirs. Pressure in the reservoirs may be managed using a simple bang-bang control technique in which the compressor servicing the positive-pressure reservoir is turned on if the pressure in the reservoir falls below a predetermined threshold and the compressor servicing the negative-pressure reservoir is turned on if the pressure in the reservoir is above a predetermined threshold. The amount of hysteresis may be the same for both reservoirs or may be different. Tighter control of the pressure in the reservoirs can be achieved by reducing the size of the hysteresis band, although this will generally result in higher cycling frequencies of the compressors. If very tight control of the reservoir pressures is required or otherwise desirable for a particular application, the bang-bang technique could be replaced with a PID control technique and could use PWM signals on the compressors.

The pressure provided by the positive-pressure reservoir is preferably strong enough—under normal conditions—to urge the membrane all the way against the rigid pumping-chamber wall. Similarly, the negative pressure (i.e., the vacuum) provided by the negative-pressure reservoir is preferably strong enough—under normal conditions—to urge the membrane all the way against the actuation-chamber wall. In a further preferred embodiment, however, these positive and negative pressures provided by the reservoirs are within safe enough limits that even with either the positive-supply valve or the negative-supply valve open all the way, the positive or negative pressure applied against the membrane is not so strong as to damage the pod pump or create unsafe fluid pressures (e.g., that may harm a patient receiving pumped blood or other fluid).

It will be appreciated that other types of actuation systems may be used to move the membrane back and forth instead of the two-reservoir pneumatic actuation system shown in FIG. 7, although a two-reservoir pneumatic actuation system is generally preferred. For example, alternative pneumatic actuation systems may include either a single positive-pressure reservoir or a single negative-pressure reservoir along with a single supply valve and a single tank pressure sensor, particularly in combination with a resilient membrane. Such pneumatic actuation systems may intermittently provide either a positive gas pressure or a negative gas pressure to the actuation chamber of the pod pump. In embodiments having a single positive-pressure reservoir, the pump may be operated by intermittently providing positive gas pressure to the actuation chamber, causing the membrane to move toward the pumping chamber wall and expel the contents of the pumping chamber, and releasing the gas pressure, causing the membrane to return to its relaxed position and draw fluid into the pumping chamber. In embodiments having a single negative-pressure reservoir, the pump may be operated by intermittently providing negative gas pressure to the actuation chamber, causing the membrane to move toward the actuation chamber wall and draw fluid into the pumping chamber, and releasing the gas pressure, causing the membrane to return to its relaxed position and expel fluid from the pumping chamber.

3. Fluid Handling

As shown and described with respect to FIGS. 2A-2D, a fluid valve in the exemplary embodiment consists of a small chamber with a flexible membrane or membrane across the center dividing the chamber into a fluid half and a pneumatic half. The fluid valve, in the exemplary embodiment, has 3 entry/exit ports, two on the fluid half of the chamber and one the pneumatic half of the chamber. The port on the pneumatic half of the chamber can supply either positive pressure or vacuum (or rather than vacuum, in some embodiments, there is a vent to atmosphere) to the chamber. When a vacuum is applied to the pneumatic portion of the chamber, the membrane is pulled towards the pneumatic side of the chamber, clearing the fluid path and allowing fluid to flow into and out of the fluid side of the chamber. When positive pressure is applied to the pneumatic portion of the chamber, the membrane is pushed towards the fluid side of the chamber, blocking the fluid path and preventing fluid flow. In the volcano valve embodiment (as shown in FIGS. 2A-2B) on one of the fluid ports, that port seals off first when closing the valve and the remainder of any fluid in the valve is expelled through the port without the volcano feature. Additionally, in one embodiment of the valves, shown in FIG. 2D, the raised feature between the two ports allows for the membrane to seal the two ports from each other earlier in the actuation stroke (i.e., before the membrane seals the ports directly).

Referring again to FIG. 7, pressure valves are used to operate the pumps located at different points in the flow path. This architecture supports pressure control by using two variable-orifice valves and a pressure sensor at each pump chamber which requires pressure control. In one embodiment, one valve is connected to a high-pressure source and the other valve is connected to a low-pressure sink. A high-speed control loop monitors the pressure sensor and controls the valve positions to maintain the necessary pressure in the pump chamber.

Pressure sensors are used to monitor pressure in the pneumatic portion of the chambers themselves. By alternating between positive pressure and vacuum on the pneumatic side of the chamber, the membrane is cycled back and forth across the total chamber volume. With each cycle, fluid is drawn through the upstream valve of the inlet fluid port when the pneumatics pull a vacuum on the pods. The fluid is then subsequently expelled through the outlet port and the downstream valve when the pneumatics deliver positive pressure to the pods.

In many embodiments pressure pumps consist of a pair of chambers. When the two chambers are run 180 degrees out of phase from one another the flow is essentially continuous.

4. Volume Measurement

These flow rates in the cassette are controlled using pressure pod pumps which can detect end-of-stroke. An outer control loop determines the correct pressure values to deliver the required flow. Pressure pumps can run an end of stroke algorithm to detect when each stroke completes. While the membrane is moving, the measured pressure in the chamber tracks a desired sinusoidal pressure. When the membrane contacts a chamber wall, the pressure becomes constant, no longer tracking the sinusoid. This change in the pressure signal is used to detect when the stroke has ended, i.e., the end-of-stroke.

The pressure pumps have a known volume. Thus, an end of stroke indicates a known volume of fluid is in the chamber. Thus, using the end-of-stroke, fluid flow may be controlled using rate equating to volume.

As described above in more detail, FMS may be used to determine the volume of fluid pumped by the metering pumps. In some embodiments, the metering pump may pump fluid without using the FMS volume measurement system, however, in the exemplary embodiments, the FMS volume measurement system is used to calculate the exact volume of fluid pumped.

5. Exemplary Embodiment of the Pumping Cassette

The terms inlet and outlet as well as first fluid, second fluid, third fluid, and the number designations given to valving paths (i.e. “first valving path”) are used for description purposes only. In other embodiments, an inlet can be an outlet, as well, an indication of a first, second, third fluid does not denote that they are different fluids or are in a particular hierarchy. The denotations simply refer to separate entrance areas into the cassette and the first, second, third, etc, fluids may be different fluids or the same fluid types or composition or two or more may be the same. Likewise, the designation of the first, second, third, etc. valving paths do not have any particular meaning, but are used for clearness of description.

The designations given for the fluid inlets (which can also be fluid outlets), for example, first fluid outlet, second fluid outlet, merely indicate that a fluid may travel out of or into the cassette via that inlet/outlet. In some cases, more than one inlet/outlet on the schematic is designated with an identical name. This merely describes that all of the inlet/outlets having that designation are pumped by the same metering pump or set of pod pumps (which in alternate embodiments, can be a single pod pump).

Referring now to FIG. 8, an exemplary embodiment of the fluid schematic of the cassette 800 is shown. Other schematics are readily discernable. The cassette 800 includes at least one pod pump 828, 820 and at least one mixing chamber 818. The cassette 800 also includes a first fluid inlet 810, where a first fluid enters the cassette. The first fluid includes a flow rate provided by one of the at least one pod pump 820, 828 in the cassette 800. The cassette 800 also includes a first fluid outlet 824 where fluid exits the cassette 800 having a flow rate provided by one of the at least one pod pump 820, 828. The cassette 800 includes at least one metering fluid line 812, 814, 816 that is in fluid connection with the first fluid outlet. The cassette also includes at least one second fluid inlet 826 where the second fluid enters the cassette 800. In some embodiments of the cassette 800 a third fluid inlet 825 is also included.

Metering pumps 822, 830 pump the second fluid and the third fluid into the first fluid outlet line. The second fluid and, in some embodiments, the third fluid, connected to the cassette 800 at the second fluid inlet 826 and third fluid inlet 825 respectively, are each fluidly connected to a metering pump 822, 830 and to the first fluid outlet line through a metering fluid line 812, 814, 816. The metering pumps 822, 830, described in more detail below, in the exemplary embodiment, include a volume measurement capacity such that the volume of fluid pumped by the metering pumps 822, 830 is readily discernable.

The mixing chamber 818 is connected to the first fluid outlet line 824 and includes a fluid inlet and a fluid outlet. In some embodiments, sensors are located upstream and downstream from the mixing chamber 818. The location of the sensors in the exemplary embodiment are shown and described below with respect to FIGS. 14C, 14D and FIGS. 15B and 15C.

The cassette 800 is capable of internally mixing a solution made up of at least two components. The cassette 800 also includes the capability of constituting a powder to a fluid prior to pumping the fluid into the mixing chamber. These capabilities will be described in greater detail below.

Various valves 832-860 impart the various capabilities of the cassette 800. The components of the cassette 800 may be used differently in the different embodiments based on various valving controls.

The fluid schematic of the cassette 800 shown in FIG. 8 may be embodied into various cassette apparatus. Thus, the embodiments of the cassette 800 including the fluid schematic shown in FIG. 8 are not the only cassette embodiments that may incorporate this or an alternate embodiment of this fluid schematic. Additionally, the types of valves, the ganging of the valves, the number of pumps and chambers may vary in various cassette embodiments of this fluid schematic.

Referring now to FIG. 8, a fluid flow-path schematic 800 is shown with the fluid paths indicated based on different valving flow paths. The fluid flow-path schematic 800 is described herein corresponding to the valving flow paths in one embodiment of the cassette. The exemplary embodiment of the midplate 900 of the cassette are shown in FIG. 10 with the valves indicated corresponding to the respective fluid flow-path schematic 800 in FIG. 8. For the purposes of the description, the fluid flow paths will be described based on the valving. The term “valving path” refers to a fluid path that may, in some embodiments, be available based on the control of particular valves. The corresponding fluid side structures of FIG. 10 are shown in FIG. 12A.

Referring now to FIGS. 8 and 10 the first valving path includes valves 858, 860. This valving path 858, 860 includes the metering fluid line 812, which connects to the second fluid inlet 826. As shown in these FIGS., in some embodiments of the cassette, there are two second fluid inlets 826. In practice, these two second fluid inlets 826 can be connected to the same fluid source or a different fluid source. Either way, the same fluid or a different fluid may be connected to each second fluid inlet 826. Each second fluid inlet 826 is connected to a different metering fluid line 812, 814.

The first of the two metering fluid lines connected to the second fluid inlet 826 is as follows. When valve 858 opens and valve 860 is closed and metering pump 822 is actuated, fluid is drawn from the second fluid inlet 826 and into metering fluid line 812. When valve 860 is open and valve 858 is closed and the metering pump 822 is actuated, second fluid continues on metering fluid line 812 into pod pump 820.

Referring now to the second valving path including valve 842, when valve 842 is open and pod pump 820 is actuated, fluid is pumped from pod pump 820 to one of the third fluid inlet 825. In one embodiment, this valving path is provided to send liquid into a container or source connected to third fluid inlet 825.

Referring now to the third valving path including valves 832 and 836 this valving path 832, 835 includes the metering fluid line 816, which connects to the third fluid inlet 825. As shown in these FIGS., in some embodiments of the cassette, there are two third fluid inlets 825. In practice, these two third fluid inlets 825 can be connected to the same fluid source or a different fluid source. Either way, the same fluid or a different fluid may be connected to each third fluid inlet 825. Each third fluid inlet 825 is connected to a different metering fluid line 862, 868.

When valve 832 opens and valve 836 is closed and metering pump 830 is actuated, fluid is drawn from the third fluid inlet 825 and into metering fluid line 830. When valve 836 is open and valve 832 is closed and the metering pump 830 is actuated, third fluid continues on metering fluid line 816 into first fluid outlet line 824.

Referring now to the fourth valving path, valve 846, when valve 846 is open and pod pump 820 is actuated, fluid is pumped from pod pump 820 to one of the third fluid inlet 825. In one embodiment, this valving path is provided to send liquid into a container or source connected to third fluid inlet 825.

Referring now to the fifth valving path, when valve 850 opens and pod pump 820 is actuated, fluid is pumped into the cassette 800 through the first fluid inlet 810, and into pod pump 820.

Referring now to the sixth valving path, when valve 838 is open and pod pump 820 is actuated, fluid is pumped from pod pump 820 to the mixing chamber 818 and to the first fluid outlet 824.

The seventh valving path includes valves 858, 856. This valving path 858, 856 includes the metering fluid line 812, which connects to the second fluid inlet 826. As shown in these FIGS., in some embodiments of the cassette, there are two second fluid inlets 826. In practice, these two second fluid inlets 826 can be connected the same fluid source or a different fluid source. Either way, the same fluid or a different fluid may be connected to each second fluid inlet 826. Each second fluid inlet 826 is connected to a different metering fluid line 812, 814.

When valve 858 opens and valve 856 is closed and metering pump 822 is actuated, fluid is drawn from the second fluid inlet 826 and into metering fluid line 812. When valve 856 is open and valve 858 is closed, and the metering pump is actuated, second fluid continues on metering fluid line 814 into pod pump 828.

Referring now to the eighth valving path, valve 848, when valve 848 is open and pod pump 828 is actuated, fluid is pumped from pod pump 828 to one of the third fluid inlet 825. In one embodiment, this valving path is provided to send fluid/liquid into a container or source connected to third fluid inlet 825.

Referring now to the ninth valving path including valve 844, when valve 844 is open and pod pump 828 is actuated, fluid is pumped from pod pump 828 to one of the third fluid inlet 825. In one embodiment, this valving path is provided to send liquid into a container or source connected to third fluid inlet 825.

Referring now to the tenth valving path, valve 848, when valve 848 is open and pod pump 828 is actuated, fluid is pumped from pod pump 828 to one of the third fluid inlet 825. In one embodiment, this valving path is provided to send fluid/liquid into a container or source connected to third fluid inlet 825.

The eleventh valving path including valves 854 and 856 is shown. This valving path 854, 856 includes the metering fluid line 814, which connects to the second fluid inlet 826. As shown in these FIGS., in some embodiments of the cassette, there are two second fluid inlets 826. In practice, these two second fluid inlets 826 can be connected the same fluid source or a different fluid source. Either way, the same fluid or a different fluid may be connected to each second fluid inlet 826. Each second fluid inlet 826 is connected to a different metering fluid line 812, 814.

The second of the two metering fluid lines connected to the second fluid inlet 826 is shown in FIG. 8. The twelfth valving path is as follows. When valve 854 opens and valve 856 is closed and metering pump 822 is actuated, fluid is drawn from the second fluid inlet 826 and into metering fluid line 814. When valve 856 is open and valve 854 is closed and the metering pump 822 is actuated, the second fluid continues on metering fluid line 814 into pod pump 828.

Similarly, the thirteenth valving path is seen when valve 854 opens and valve 860 is closed and metering pump 822 is actuated, fluid is drawn from the second fluid inlet 826 and into metering fluid line 814. When valve 860 is open and valve 854 is closed, and the metering pump 822 is actuated, the second fluid continues on metering fluid line 814 into pod pump 820.

Referring now to the fourteenth valving path including valve 852. When valve 852 opens and pod pump 828 is actuated, fluid is pumped into the cassette 800 through the first fluid inlet 810, and into pod pump 828.

Referring now to the fifteenth valving path, when valve 840 is open and pod pump 828 is actuated, fluid is pumped from pod pump 828 to the mixing chamber 818 and to the first fluid outlet 824. The sixteenth valving path including valve 834, when valve 834 is open and valve 836 opens, and the metering pump 830 is actuated, fluid from the third fluid inlet 825 flows on metering fluid line 862 and to metering fluid line 816.

In the exemplary fluid flow-path embodiment shown in FIG. 8, and corresponding structure of the cassette shown in FIG. 10, valves are open individually. In the exemplary embodiment, the valves are pneumatically open. Also, in the exemplary embodiment, the fluid valves are volcano valves, as described in more detail in this specification.

Referring now to FIGS. 11A-11B, the top plate 1100 of exemplary embodiment of the cassette is shown. In the exemplary embodiment, the pod pumps 820, 828 and the mixing chambers 818 on the top plate 1100, are formed in a similar fashion. In the exemplary embodiment, the pod pumps 820, 828 and mixing chamber 818, when assembled with the bottom plate, have a total volume of capacity of 38 ml. However, in other embodiments, the mixing chamber can have any size volume desired.

Referring now to FIG. 11B, the bottom view of the top plate 1100 is shown. The fluid paths are shown in this view. These fluid paths correspond to the fluid paths shown in FIGS. 12A-12B in the midplate 1200. The top plate 1100 and the top of the midplate 1200 form the liquid or fluid side of the cassette for the pod pumps 820, 828 and for one side of the mixing chamber 818. Thus, most of the liquid flow paths are on the top 1100 and midplates 1200. Referring to FIG. 12B, the first fluid inlet 810 and the first fluid outlet 824 are shown.

Still referring to FIGS. 11A and 11B, the pod pumps 820, 828 include a groove 1002 (in alternate embodiments, this is a groove). The groove 1002 is shown having a particular size and shape, however, in other embodiments, the size and shape of the groove 1002 can be any size or shape desirable. The size and shape shown in FIGS. 11A and 11B is the exemplary embodiment. In all embodiments of the groove 1002, the groove 1002 forms a path between the fluid inlet side and the fluid outlet side of the pod pumps 820, 828. In alternate embodiments, the groove 1002 is a groove in the inner pumping chamber wall of the pod pump.

The groove 1002 provides a fluid path whereby when the membrane is at the end-of-stroke there is still a fluid path between the inlet and outlet such that the pockets of fluid or air do not get trapped in the pod pump. The groove 1002 is included in both the liquid/fluid and air/actuation sides of the pod pumps 820, 828. In some embodiments, the groove 1002 may also be included in the mixing chamber 818 (see FIGS. 13A-13B with respect to the actuation/air side of the pod pumps 820, 828 and the opposite side of the mixing chamber 818. In alternate embodiments, the groove 1002 is either not included or on only one side of the pod pumps 820, 828.

In an alternate embodiment of the cassette, the liquid/fluid side of the pod pumps 820, 828 may include a feature (not shown) whereby the inlet and outlet flow paths are continuous and a rigid outer ring (not shown) is molded about the circumference of the pumping chamber is also continuous. This feature allows for the seal, formed with the membrane (not shown) to be maintained. Referring to FIG. 11E, the side view of the exemplary embodiment of the top plate 1100 is shown.

Referring now to FIGS. 12A-12B, the exemplary embodiment of the midplate 1200 is shown. The midplate 1200 is also shown in FIGS. 9A-9F and 10A-10F, where these FIGS. correspond with FIGS. 12A-12B. Thus, FIGS. 9A-9F and 10A-10F indicate the locations of the various valves and valving paths. The locations of the membranes (not shown) for the respective pod pumps 820, 828 as well as the location of the mixing chamber 818 are shown.

Referring now to FIG. 12A, in the exemplary embodiment of the cassette, sensor elements are incorporated into the cassette so as to discern various properties of the fluid being pumped. In one embodiment, three sensor elements are included. However, in the exemplary embodiment, six sensor elements (two sets of three) are included. The sensor elements are located in the sensor cell 1314, 1316. In this embodiment, a sensor cell 1314, 1316 is included as an area on the cassette for sensor(s) elements. In the exemplary embodiment, the three sensor elements of the two sensor cells 1314, 1316 are housed in respective sensor elements housings 1308, 1310, 1312 and 1318, 1320, 1322. In the exemplary embodiment, two of the sensor elements housings 1308, 1312 and 1318, 1320 accommodate a conductivity sensor elements and the third sensor elements housing 1310, 1322 accommodates a temperature sensor elements. The conductivity sensor elements and temperature sensor elements can be any conductivity or temperature sensor elements in the art. In one embodiment, the conductivity sensors are graphite posts. In other embodiments, the conductivity sensor elements are posts made from stainless steel, titanium, platinum or any other metal coated to be corrosion resistant and still be electrically conductive. The conductivity sensor elements will include an electrical lead that transmits the probe information to a controller or other device. In one embodiment, the temperature sensor is a thermister potted in a stainless steel probe. However, in alternate embodiments, a combination temperature and conductivity sensor elements is used similar to the one described U.S. patent application entitled Sensor Apparatus Systems, Devices and Methods filed Oct. 12, 2007 (DEKA-024XX).

In alternate embodiments, there are either no sensors in the cassette or only a temperature sensor, only one or more conductivity sensors or one or more of another type of sensor.

Referring now to FIG. 12C, the side view of the exemplary embodiment of the midplate 1200 is shown. Referring now to FIGS. 13A-13B, the bottom plate 1300 is shown. Referring first to FIG. 13A, the inner or inside surface of the bottom plate 1300 is shown. The inner or inside surface is the side that contacts the bottom surface of the midplate (not shown, see FIG. 12B). The bottom plate 1300 attaches to the air or actuation lines (not shown). The corresponding entrance holes for the air that actuates the pod pumps 820, 828 and valves (not shown, see FIGS. 10A-10F) in the midplate 1200 can be seen. Holes 810, 824 correspond to the first fluid inlet and first fluid outlet shown in FIGS. 12B, 810, 824 respectively. The corresponding halves of the pod pumps 820, 828 and mixing chamber 818 are also shown, as are the grooves 1002 for the fluid paths. The actuation holes in the pumps are also shown. Unlike the top plate, the bottom plate 1300 corresponding halves of the pod pumps 820, 828 and mixing chamber 818 make apparent the difference between the pod pumps 820, 828 and mixing chamber 818. The pod pumps 820, 828 include an air/actuation path on the bottom plate 1300, while the mixing chamber 818 has identical construction to the half in the top plate. The mixing chamber 818 mixes liquid and therefore, does not include a membrane (not shown) nor an air/actuation path. The sensor cell 1314, 1316 with the three sensor element housings 1308, 1310, 1312 and 1318, 1320, 1322 are also shown.

Referring now to FIG. 13B, the actuation ports 1306 are shown on the outside or outer bottom plate 1300. An actuation source is connected to these actuation ports 1306. Again, the mixing chamber 818 does not have an actuation port as it is not actuated by air. Referring to FIG. 13C, a side view of the exemplary embodiment of the bottom plate 1300 is shown.

5.1 Membranes

In the exemplary embodiment, the membrane is a gasket o-ring membrane as shown in FIG. 5A. However, in some embodiments, a gasket o-ring membranes having texture, including, but not limited to, the various embodiments in FIG. 4D, or 5B-5D may be used. In still other embodiments, the membranes shown in FIGS. 6A-6G may also be used.

Referring next to FIGS. 14A and 14B, the assembled exemplary embodiment of the cassette 1400 is shown. FIGS. 14C and 14D are an exploded view of the exemplary embodiment of the cassette 1400. The membranes 1600 are shown. As can be seen from FIGS. 14C and 14D, there is one membrane 1602 for each of the pods pumps. In the exemplary embodiment, the membrane for the pod pumps is identical. In alternate embodiments, any membrane may be used, and one pod pump could use one embodiment of the membrane while the second pod pump can use a different embodiment of the membrane (or each pod pump can use the same membrane).

The various embodiments of the membrane used in the metering pumps 1604, in the preferred embodiment, are shown in more detail in FIGS. 5E-5H. The various embodiments of the membrane used in the valves 1222 is shown in more detail in FIGS. 2E-2G. However, in alternate embodiments, the metering pump membrane as well as the valve membranes may contain textures for example, but not limited to, the textures shown on the pod pump membranes shown in FIGS. 5A-5D.

One embodiment of the conductivity sensor elements 1314, 1316 and the temperature sensor element 1310, which make up the sensor cell 1322, are also shown in FIGS. 14C and 14D. Still referring to FIGS. 14C and 14D, the sensor elements are housed in sensor blocks (shown as 1314, 1316 in FIGS. 12B and 13A) which include areas on the bottom plate 1300 and the midplate 1200. O-rings seal the sensor housings from the fluid lines located on the upper side of the midplate 1200 and the inner side of the top plate 1100. However, in other embodiments, an o-ring is molded into the sensor block or any other method of sealing can be used.

5.2 Cross Sectional Views

Referring now to FIGS. 15A-15C, various cross sectional views of the assembled cassette are shown. Referring first to FIG. 15A, the membranes 1602 are shown in a pod pumps 820, 828. As can be seen from the cross section, the o-ring of the membrane 1602 is sandwiched by the midplate 1200 and the bottom plate 1300. A valve membrane 1606 can also be seen. As discussed above, each valve includes a membrane.

Referring now to FIG. 15B, the two conductivity sensors 1308, 1312 and the temperature sensor 1310 are shown. As can be seen from the cross section, the sensors 1308, 1310, 1312 are in the fluid line 824. Thus, the sensors 1308, 1310, 1312 are in fluid connection with the fluid line and can determine sensor data of the fluid exiting fluid outlet one 824. Still referring to FIG. 15B, a valve 836 cross section is shown. As shown in this FIG., in the exemplary embodiment, the valves are volcano valves similar to the embodiment shown and described above with respect to FIG. 2B. However, as discussed above, in alternate embodiment, other valves are used including, but not limited, to those described and shown above with respect to FIGS. 2A, 2C and 2D.

Referring now to FIG. 15C, the two conductivity sensor elements 1318, 1320 and the temperature sensor element 1322 are shown. As can be seen from the cross section, the sensor elements 1318, 1320, 1322 are in the fluid line 824. Thus, the sensor elements 1318, 1320, 1322 are in fluid connection with the fluid line and can be used to determine sensor data of the fluid entering the mixing chamber (not shown in this figure).

Thus, in the exemplary embodiment, the sensor elements 1318, 1320, 1322 are used to collect data regarding fluid being pumped into the mixing chamber. Referring back to FIG. 12B, sensor elements 1308, 1310, 1312 are used to collect data regarding fluid being pumped from the mixing chamber and to the fluid outlet. However, in alternate embodiments, no sensors are or only one set, or only one type of sensor element (i.e., either temperature or conductivity sensor element) is used. Any type of sensor may be used and additionally, any embodiment of a temperature, a conductivity sensor element or a combined temperature/conductivity sensor element.

As described above, the exemplary embodiment is one cassette embodiment that incorporates the exemplary fluid flow-path schematic shown in FIG. 8. However, there are alternate embodiments of the cassette that incorporate many of the same features of the exemplary embodiment, but in a different structural design and with slightly different flow paths. One of these alternate embodiments is the embodiment shown in FIGS. 16A-20B.

Referring now to FIGS. 16A-16C, views of an alternate embodiment of the top plate 1600 are shown. The features of the top plate 1600 are alternate embodiments of corresponding features in the exemplary embodiment. This alternate embodiment includes two mixing chambers 1622, 1624 and three metering pumps. Thus, this embodiment represents the flexibility in the cassette design. In various embodiments, the cassette can mix any number of fluids, as well, can meter them separately or together. FIG. 9 shows a fluid flow-path schematic of the cassette shown in FIGS. 16A-20B.

Referring now to FIGS. 17A-17C, views of an alternate embodiment of the midplate 1700 are shown. FIGS. 18A-18C show views of an alternate embodiment of the bottom plate 1800.

Referring now to FIG. 19A, an assembled alternate embodiment of the cassette 1900 is shown. FIGS. 19C-19D show exploded views of the cassette 1900 where the pod pump membranes 1910, valve membranes 1914 and metering pump membranes 1912 are shown. The three metering pumps 1616, 1618, 1620 can be seen as well as the respective membranes 1912. In this embodiment, three fluids can be metered and controlled volumes of each can be mixed together in the mixing chambers 1622, 1624. FIGS. 20A and 20B show a cross sectional view of the assembled cassette 1900.

As this alternate embodiment shows, there are many variations of the pumping cassette and the general fluid schematic shown in FIG. 8. Thus, additional mixing chambers and metering pumps can add additional capability to the pumping cassette to mix more than two fluids together.

5.3 Exemplary Embodiments of the Pumping Cassette

In practice, the cassette may be used to pump any type of fluid from any source to any location. The types of fluid include nutritive, normutritive, inorganic chemicals, organic chemicals, bodily fluids or any other type of fluid. Additionally, fluid in some embodiments includes a gas, thus, in some embodiments; the cassette is used to pump a gas.

The cassette serves to pump and direct the fluid from and to the desired locations. In some embodiments, outside pumps pump the fluid into the cassette and the cassette pumps the fluid out. However, in some embodiments, the pod pumps serve to pull the fluid into the cassette and pump the fluid out of the cassette.

As discussed above, depending on the valve locations, control of the fluid paths is imparted. Thus, the valves being in different locations or additional valves are alternate embodiments of this cassette. Additionally, the fluid lines and paths shown in the figures described above are mere examples of fluid lines and paths. Other embodiments may have more, less and/or different fluid paths. In still other embodiments, valves are not present in the cassette.

The number of pod pumps described above may also vary depending on the embodiment. For example, although the exemplary and alternate embodiments shown and described above include two pod pumps, in other embodiments, the cassette includes one. In still other embodiments, the cassette includes more than two pod pumps. The pod pumps can be single pumps or work in tandem to provide a more continuous flow. Either or both may be used in various embodiments of the cassette.

The various ports are provided to impart particular fluid paths onto the cassette. These ports are not necessarily all used all of the time, instead, the variety of ports provide flexibility of use of the cassette in practice.

The pumping cassette can be used in a myriad of applications. However, in one exemplary embodiment, the pumping cassette is used to mix a solution that includes at least two ingredients/compounds. In the exemplary embodiment, three ingredients are mixed. However, in other embodiments, less than three or more than three can be mixed by adding metering pumps, mixing chambers, inlets/outlets, valves and fluid lines. These variations to the cassette design are readily discernable.

As used herein, the terms “source ingredient” or “sources of ingredients” refers to ingredients other than the fluid pumped into the cassette from the first fluid inlet. These source ingredients are contained in a container, or provided by a source, connected to the cassette.

In the exemplary embodiment, the pumping cassette includes the ability to connect four sources of ingredients to the cassette in addition to the fluid inlet line. In the exemplary embodiment, the fluid inlet is connected to a water source. However, in other embodiments, the fluid inlet line is connected to a container of a liquid/fluid solution or to another source of fluid/liquid.

In the exemplary embodiment, the four additional sources of ingredients can be four of the same source ingredients, or two of one source ingredient and two of another. Using two of each source ingredient, or four of one source ingredient, pumping and mixing can be done in a continuous manner without having to replace the sources. However, depending on the source, the number of redundant sources of each ingredient will vary. For example, the source could be a connection to a very large container, a smaller container or a seemingly “endless” source. Thus, depending on the volume being pumped and the size of the source, the number of containers of a source ingredient may vary.

One of the fluid paths described above with respect to FIG. 8 includes a path where the pod pumps pump liquid into the cassette and to two of the source ingredients sources or containers. This available functionality of the cassette allows two of the source ingredients to be, at least initially, powder that is constituted with the fluid/liquid from the fluid inlet line. As well, there is a valving path for both pod pumps that can accomplish pumping fluid to the ingredient sources. Thus, in one embodiment, the valves are controlled for a period of time such that continuous pumping of fluid into the fluid inlet and to two source ingredient containers is accomplished. This same valving path can be instituted to the other two source ingredient containers or to one of the other two source ingredient containers in addition to or in lieu of the valving path shown in FIG. 8. In other embodiments, fluid inlet liquid is pumped to only one source ingredient container.

Additionally, in some embodiments, fluid is pumped into the fluid inlet and to the source ingredients where the source ingredients are fluid. This embodiment may be used in situations where the fluid inlet fluid is a source ingredient that needs to be mixed with one of the source ingredients prior to pumping. This functionality can be designed into any embodiment of the pumping cassette. However, in some embodiments, this valving path is not included.

In the exemplary embodiment, the metering pumps allow for the pumping of the source ingredients in known volumes. Thus, careful pumping allows for mixing a solution requiring exact concentrations of the various ingredients. A single metering pump could pump multiple source ingredients. However, as an ingredient is pumped, small amounts of that ingredient may be present in the metering fluid line and thus, could contaminate the ingredient and thus, provide for an incorrect assessment of the volume of that second ingredient being pumped. Therefore, in the exemplary embodiment, at least one metering pump is provided for each source ingredient, and thus, a single metering pump is provided for two sources of source ingredients where those two sources contain identical source ingredients.

In the exemplary embodiment, for each source ingredient, a metering pump is provided. Thus, in embodiments where more than two source ingredients are present, additional metering pumps may be included for each additional source ingredient in the pumping cassette. In the exemplary embodiment, a single metering pump is connected to two source ingredients because in the exemplary embodiment, these two source ingredients are the same. However, in alternate embodiments, one metering pump can pump more than one source ingredient and be connected to more than one source ingredient even if they are not the same.

Sensors or sensor elements may be included in the fluid lines to determine the concentration, temperature or other characteristic of the fluid being pumped. Thus, in embodiments where the source ingredient container included a powder, water having been pumped by the cassette to the source ingredient container to constitute the powder into solution, a sensor could be used to ensure the correct concentration of the source ingredient. Further, sensor elements may be included in the fluid outlet line downstream from the mixing chamber to determine characteristics of the mixed solution prior to the mixed solution exiting the cassette through the fluid outlet. Additionally, a downstream valve can be provided to ensure badly mixed solution is not pumped outside the cassette through the fluid outlet. Discussion of the exemplary embodiment of the sensor elements is included above.

One example of the pumping cassette in use is as a mixing cassette as part of a hemodialysis system. The mixing cassette would be used to mix dialysate to feed a dialysate reservoir outside the cassette. Thus, the cassette would be connected to two containers of each citric acid and NaCl/bicarbonate. Two metering pumps are present in the cassette, one dedicated to the citric acid and the other to the NaCl/Bicarbonate. Thus, one metering pump works with two source ingredient containers.

In the exemplary embodiment, the NaCl/Bicarbonate is a powder and requires the addition of water to create the fluid source ingredient solution. Thus, water is pumped into the first fluid inlet and into the source containers of NaCl/Bicarbonate. Both pod pumps can pump out of phase to rapidly and continuously provide the necessary water to the source containers of NaCl/Bicarbonate.

To mix the dialysate, the citric acid is pumped by a metering pump into a pod pump and then towards the mixing chamber. Water is pumped into the pod pumps as well, resulting in a desired concentration of citric acid. Sensor elements are located upstream from the mixing chamber to determine if the citric acid is in the proper concentration and also, the pod pumps can pump additional water towards the mixing chamber if necessary to achieve the proper concentration.

The NaCl/Bicarbonate is pumped by the second metering pump and into the fluid outlet line upstream from the mixing chamber. The citric acid and fluid NaCl/Bicarbonate will enter the mixing chamber. The two source ingredients will then mix and be pumped out the fluid outlet.

In some embodiments, sensor elements are located downstream from the mixing chamber. These sensor elements can ensure the concentration of the finished solution is proper. Also, in some embodiments, a valve may be located downstream from the fluid outlet. In situations where the sensor data shows the mixing has not been successful or as desired, this valve can block the dialysate from flowing into the reservoir located outside the cassette.

In alternate embodiments of the cassette, addition metering pumps can be includes to remove fluid from the fluid lines. Also, additional pod pumps may be included for additional pumping features. In alternate embodiments of this dialysate mixing process, three metering pumps and two mixing chambers are used (as shown in FIG. 9). The citric acid, salt, and bicarbonate are each pumped separately in this embodiment. One mixing chamber is similar to the one described above, and the second mixing chamber is used to mix the salt and bicarbonate prior to flowing to the other mixing chamber, where the mixing between the citric acid, NaCl/Bicarbonate will be accomplished.

Various embodiments of the cassette for mixing various solutions are readily discernable. The fluid lines, valving, metering pumps, mixing chambers, pod pumps and inlet/outlets are modular elements that can be mixed and matched to impart the desired mixing functionality onto the cassette.

In various embodiments of the cassette, the valve architecture varies in order to alter the fluid flow-path. Additionally, the sizes of the pod pumps, metering pump and mixing chambers may also vary, as well as the number of valves, pod pumps, metering pumps, sensors, mixing chambers and source ingredient containers connected to the cassette. Although in this embodiment, the valves are volcano valves, in other embodiments, the valves are not volcano valves and in some embodiments are smooth surface valves.

While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention. 

1. A pump cassette comprising: a housing; a first pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a first pump inlet and a first pump outlet, the first pump inlet in valved fluid communication with a first fluid port in the housing; a mixing chamber in the housing having an inlet in valved fluid communication with the first pump outlet and an outlet in valved fluid communication with a second fluid port in the housing; and a first conductivity sensing flow path arranged to connect the outlet of the first pump with a first conductivity sensor apparatus configured to measure a conductivity of a fluid contained in the first conductivity sensing flow path.
 2. The pump cassette of claim 1, further comprising: a second pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane and having a second pump inlet in valved fluid communication with a third fluid port in the housing and a second pump outlet in valved fluid communication with the inlet of the mixing chamber.
 3. The pump cassette of claim 2, further comprising: a third pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane and having a third pump inlet in valved fluid communication with a fourth fluid port in the housing and a third pump outlet in valved fluid communication with the inlet of the mixing chamber; and a second conductivity sensing flow path arranged to connect the outlet of the mixing chamber with a second conductivity sensor apparatus configured to measure a conductivity of a fluid contained in the second conductivity sensing flow path.
 4. The pump cassette of claim 3, wherein the cassette is configured to connect with a pressure source to operate the first pump, to connect with first, second, and third fluid sources via the first, third and fourth fluid ports in the housing to mix first, second and third fluids to create a mixed fluid stream and to connect via the second fluid port in the housing to a destination for the mixed fluid stream.
 5. The pumping cassette of claim 1, wherein the mixing chamber comprises a fluid pumping chamber of a second pump in the housing, the second pump comprising an actuation chamber separated from the fluid pumping chamber by a flexible membrane.
 6. The pumping cassette of claim 2, wherein the mixing chamber has a fixed volume that is substantially the same as a maximum volume of the fluid pumping chamber of second pump.
 7. The pumping cassette of claim 3, further comprising the first conductivity sensing apparatus and the second conductivity sensing apparatus, and wherein the first conductivity sensing flow path, first conductivity sensing apparatus, second conductivity sensing flow path, and second conductivity sensing apparatus are contained within the housing.
 8. The pumping cassette of claim 1, wherein the housing comprises a stacked arrangement of a top plate, a bottom plate, and a midplate positioned between the top plate and the bottom plate.
 9. The pump cassette of claim 1 wherein the first pump comprises a curved rigid fluid-pumping chamber wall, and wherein the actuation chamber comprises a port for delivering pressure to the flexible membrane to effect fluid pumping.
 10. The pump cassette of claim 1, wherein the valved fluid communications comprise membrane-based valves, each valve having a flexible membrane, one side of which is configured and positioned to interrupt fluid flow through the valve upon application of pressure to an opposing side of the membrane.
 11. The pump cassette of claim 3, wherein each of the first and third pumps has a maximum pumping volume that is smaller than a maximum pumping volume of the second pump.
 12. The pump cassette of claim 4, further comprising a fourth pump in the housing having an inlet in valved fluid communication with the third fluid port in the housing, and an outlet in valved fluid communication with a fifth fluid port in the housing, wherein the fifth fluid port is configured to connect to the first or the second fluid source.
 13. The pump cassette of claim 7, wherein a flow path within the housing connecting the outlet of the second pump with the inlet of the mixing chamber comprises the first conductivity sensor apparatus, and the flow path within the cassette connecting the outlet of the mixing chamber with the second fluid port in the housing comprises the second conductivity sensor apparatus.
 14. The pumping cassette of claim 1, further comprising the first conductivity sensing apparatus, and wherein the first conductivity sensing flow path and first conductivity sensing apparatus are contained within the housing.
 15. A pump cassette comprising: a housing; a first pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a first pump inlet and a first pump outlet, the first pump inlet in valved fluid communication with a first fluid port in the housing; a second pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a second pump inlet connected to a second fluid port in the housing and a second pump outlet in valved fluid communication with the first pump inlet; a third pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a third pump inlet connected to a third fluid port in the housing and a third pump outlet in valved fluid communication with the first pump outlet; a mixing chamber in the housing having an inlet in valved fluid communication with the first pump outlet and an outlet in valved fluid communication with a fourth fluid port in the housing; a first conductivity sensing flow path arranged to connect the outlet of the first pump with a first conductivity sensor apparatus configured to measure a conductivity of a fluid contained in the first conductivity sensing flow path; and a second conductivity sensing flow path arranged to connect the outlet of the mixing chamber with a second conductivity sensor apparatus configured to measure a conductivity of a fluid contained in the first conductivity sensing flow path.
 16. The pump cassette of claim 15, wherein the valved fluid communications comprise membrane-based valves, each valve having a flexible membrane, one side of which is configured and positioned to interrupt fluid flow through the valve upon application of pressure to an opposing side of the membrane.
 17. The pump cassette of claim 15, further comprising the first conductivity sensing apparatus and the second conductivity sensing apparatus, and wherein the first conductivity sensing flow path, first conductivity sensing apparatus, second conductivity sensing flow path, and second conductivity sensing apparatus are contained within the housing.
 18. A pump cassette comprising: a housing; a first pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a first pump inlet and a first pump outlet, the first pump inlet in valved fluid communication with a first fluid port in the housing; a second pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a second pump inlet connected to a second fluid port in the housing and a second pump outlet in valved fluid communication with the first pump inlet; a third pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a third pump inlet connected to a third fluid port in the housing and a third pump outlet in valved fluid communication with the first pump outlet; a fourth pump in the housing comprising a fluid-pumping chamber separated from an actuation chamber by a flexible membrane, the fluid-pumping chamber having a fourth pump inlet in valved fluid communication with the first fluid port in the housing, and a fourth pump outlet in valved fluid communication with a fifth fluid port in the housing; a mixing chamber in the housing having an inlet in valved fluid communication with the first pump outlet and an outlet in valved fluid communication with a fourth fluid port in the housing; a first conductivity sensing flow path arranged to connect the outlet of the first pump with a first conductivity sensor apparatus; and a second conductivity sensing flow path arranged to connect the outlet of the mixing chamber with a second conductivity sensor apparatus; wherein the valved fluid communications comprise membrane-based valves, each valve having a flexible membrane, one side of which is configured and positioned to interrupt fluid flow through the valve upon application of pressure to an opposing side of the membrane.
 19. The pump cassette of claim 18, further comprising the first conductivity sensing apparatus and the second conductivity sensing apparatus, and wherein the first conductivity sensing flow path, first conductivity sensing apparatus, second conductivity sensing flow path, and second conductivity sensing apparatus are contained within the housing. 